Brightening nickel



Patented MaylZ, 1953 BaiGHTENING Nickel Walter G. Zelley, NewKensington, Pa assignor to Aluminum Company of'America, Pittsburgh,

Pa., a corporation of Pennsylvania" inoinrtwsi. Application January16,1951, Serial No. 206,314 51 j.

This invention relates tov solutions and methods for the chemicalbrightening of nickel. As used herein, the term nickel includes purevnickel, commercial nickel containing the usualimpurities, nickel basealloys, and nickel plated upon other metals.

According to my invention, nickel surfaces may be readily brightened bysimply immersing them for a short time in certain hot aqueous solutionscontaining phosphoric acid, sulfuric acid and nitric acid.

In the past bright nickel plated surfaces have usually been produced inso-called bright nickel baths, or by bufiing the nickel plates producedin s o-called dull or semi-bright nickel baths. Bright nickel baths aredifiicult to maintain in satisfactory condition and do not producenickel plates having all the desired properties of the other types ofbaths. On the other hand, bufling is an expensive finishing procedure,and also is not conveniently employed for treatin small articles or avariety of different articles. Many efforts have been made to brightennickel and nickel plated surfaces in simple chemical solutions, but fewsuch treatments have been successful, particularly for the production ofsurfaces which are both smooth and bright.

An object of this invention is to provide a convenient method forbrightening nickel surfaces, particularly nickel plated surfaces.Another object is to provide a simple chemical solution and method forbrightening nickel surfaces, thus minimizing or eliminating the need forbufling of such surfaces. These and other objects will be apparent inthe following description of the in vention.

The solutions that may be employed in accord ance with the inventionmust comprise, as the essential component thereof, on a weight basisreferred to the total weight of phosphoric acid, sulfuric acid, nitricacid and water therein, about 45 to 60 per cent phosphoric acid (H3PO4),about to per cent sulfuric acid (HzSOi) about 8 to 15 per cent nitricacid (HNOs) and. about 10 to 20 per cent water (H2O). The stated watercontent of the solutions just referred to, and also of those hereinafterreferred to, is the entire water content thereof, whether added with theother components or separately. For optimum results such solutionscomprising about to per cent phosphoric acid, about 18 to 23 per centsulfuric acid, about 10 to 13 per cent nitric acid and about 12 to 18per cent water should be employed.

A solution consisting essentially of the four 5 Claims. (o1.- 41-421)components specified above, within the limits.

stated, is very effective for brightening nickel surfaces. However, asolution in which the components specified above constitute but apredominant part of the total is also contemplated. Limited amounts ofimpurities, dissolved metals.

or other components may be contained in the solution, for example.

The composition of the solution and the temperature at which it isemployed are very important. It is only when phosphoric acid, sulfuricacid and nitric acid are mixed in certain proportions, with anappropriate amount of water, that a brightening solution for nickel isproduced. Further it is only when such a solution is employed attemperatures above about C. that it is effective for improving thebrightness and smoothness of nickel surfaces. To obtain the best resultsthe solution used should be moderately agitated and maintained at atemperature between about and 90 C.

The period of immersion will vary with the type of nickel being treatedand the temperature of the solution. Generally from about 1 minute to 3minutes is adequate to effect the removal of about 0.0002 to 0.0003inches of nickel from the surface being treated, and thus effect goodpolishing thereof. Shorter periods of time are often sufficient; andlonger periods of time may be employed, but do not appear to producesuperior results. A single immersion in the solution is, of course,ordinarily sufiicient.

Surfaces of various types of nickel may be treated in the solution withbeneficial results. Surfaces of high brilliancy and smoothness areobtained on nickel plates, for example, thus facilitating the'productionof smooth plates superimposed thereon.

A typical solution for use in accordance with the invention contains thefollowing components:

Per cent by weight H3PO4 52 H2804 21 HNOs 12 H2O 15 Such a solution maybe readily made up from reagent strength acids, as follows:

Milliliters per liter Phosphoric acid 600 Sulfuric acid (96%) 200 Nitricacid (70%) 2 0 in which case no added water is required.

During use of the solutions described, various components may bevolatilized or decomposed, but the solutions may be readilyre-constituted by appropriate additions of components which have reachedtoo low a concentration. Nitric acid additions, for example, must bemade from time to time in order to replace amounts which are used up.

It will be understood that brightened nickel surfaces produced inaccordance with the invention may be suitably protected by lacquers,employed as a base for chrome plating thereoven or used directly asmade.

I claim:

1. A method for chemical brightening-o1 nickel which comprises immersinga nickel article in a solution consisting essentially of a about .45 to60 per cent phospheric acid, about '15 to 25 per cen sulfuric acid,about 8 to per cent nitric acid and about 10 to per cent water, on aweight basis referred to the total Weight of the aforemid components,the solution bemg maintained at a temperature above about v.65 C.

2. A method for chemical brightening of nickel which comprises immersinga nickle article a solution consisting essentially of about'fio to percent phosphoric acid, about 18 to 23 per cent sulfuric acid, about v10to 13 per cent nitric acid 4 and about 12 to 18 per cent water, on aweight basis referred to the total weight of the aforesaid components,the solution being maintained at a temperature between about 15 and 90C.

3. A method according to claim 1 wherein the article is immersed for aperiod of about 1 to 33mm.

$1. method according to claim 2 wherein the article is immersed for aperiod of about 1 to V3 vminutes.

5. A method for chemical brightening of nickel which comprises immersinga nickel article for about 11 to :3 minutes in a solution Consisting oiabout :52 :per cent :phosphoric acid, about 21 p cent isulmric :acid,about 12 per cent nitric acid and 15 per cent water, on a Weight basis,the solution being maintained at a temperature between about and C.

WALTER G. ZELLEY.

Reicrenccs Cited in the file of this patent UNITED STATES PATENTS NumberName Date 25 $154355 Kepier M Apr. 1-8, 1939 2,337,062 Page 'Dec. 21,1943 2,434,021 Thompson et a1. Jan. 6, I948

1. A METHOD FOR CHEMICAL BRIGHTENING OF NICKEL WHICH COMPRISES IMMERSINGA NICKEL ARTICLE IN A SOLUTION CONSISTING ESSENTIALLY OF ABOUT 45 TO 60PER CENT PHOSPHERIC ACID, ABOUT 15 TO 25 PER CENT SULFURIC ACID, ABOUT 8TO 15 PER CENT NITRIC ACID AND ABOUT 10 TO 20 PER CENT WATER, ON AWEIGHT BASIS REFERRED TO THE TOTAL WEIGHT OF THE AFORESAID COMPONENTS,THE SOLUTION BEING MAINTAINED AT A TEMPERATURE ABOVE ABOUT 65* C.